Sumi Tokiwadai is a central character in the visual novel 'Monobeno.' She is a young girl with a mysterious past who becomes deeply involved in the game's unfolding events. Sumi is known for her sweet and gentle personality, yet she harbors an enigmatic aura that draws the protagonist into a world of fantasy and intrigue. Her role in the series is pivotal, as she helps unravel the mysteries surrounding the town of Monobeno and its supernatural occurrences, while her interactions with the protagonist explore themes of growth and understanding.